Process for curing a polymerizable composition

ABSTRACT

By means of a curing process combining thermal and UV curing it is possible, using compositions comprising (A) a coating system based on a polyacrylate polyol or polyester polyol with melamine, or a polyacrylate polyol and/or polyester polyol with a blocked or unblocked polyisocyanate, or a carboxyl-, anhydride- or amino-functional polyester and/or polyacrylate with an epoxy-functional polyester or polyacrylate, (B) an OH—, NH 2 —, COOH—, epoxy- or NCO-functional resin containing, in addition, at least one ethylenically unsaturated double bond, which is separated from the functional group by a spacer group, and (C) at least one photoinitiator, to obtain coatings having good surface properties.

[0001] The invention relates to a process for the curing of surfacecoatings, whereby the surface hardness of the cured surface coating isincreased by means of irradiation with UV light, and to a polymerisablecomposition.

[0002] In U.S. Pat. No. 4,121,965 the resistance of thermoplasticpolyurethane surfaces to solvents and abrasion is improved by treatmentof the surface with a mixture of solvent and photoinitiator and bysubsequent irradiation with UV light. Derwent No. 94-252879/31 (JP-A Hei6 184267) describes a polyurethane resin obtained by reacting polyolmixtures, containing chlorinated polyols and polyols having COOH groups,with polyisocyanates and unsaturated monohydroxy compounds and, whereappropriate, a photoinitiator. DE-A 42 37 659 claims surface-coatingcompositions that contain functionalised resins having α,β-unsaturatedgroups and that are cured thermally. Derwent No. 87-331357 (JP-A Sho 62236867) describes a curing process combining thermal and photochemicalcuring. Derwent No. 85-188037 (JP-A Sho 60 118271) discloses a combinedheat- and UV-curable composition. EP-A 600 262 claims photoresistcompositions having heat- and UV-curable components. In DE-A 33 32 004and EP-A 247 563 there are prepared UV-curable surface-coating systemsthat comprise epoxide/amine- or polyol/isocyanate-based resins.

[0003] In the art there is a need for resins for coatings and surfacecoatings that exhibit good properties especially in respect of thedurability of the cured surface.

[0004] It has now been found, surprisingly, that coatings having verygood surface properties can be obtained by means of a process for thecuring of a polymerisable composition comprising

[0005] (A) a coating system based on

[0006] (I) a polyacrylate polyol and/or polyester polyol with melamineor

[0007] (II) a polyacrylate polyol and/or polyester polyol with a blockedor unblocked polyisocyanate or

[0008] (Ill) a carboxyl-, anhydride- or amino-functional polyesterand/or polyacrylate with an epoxy-functional polyester or polyacrylate,or

[0009] (IV) a mixture of (I), (II), (III) and/or (IV),

[0010] (B) an OH—, NH₂—, COOH—, epoxy- or NCO-functional resincontaining, in addition, at least one ethylenically unsaturated doublebond, it being necessary for a spacer group of at least 4 linearlylinked atoms to be present between the double bond and the functionalgroup,

[0011] wherein components (A) and (B) do not contain halogen, and

[0012] (C) at least one photoinitiator,

[0013] by thermal treatment and, for the purpose of improving thesurface properties, subsequent photochemical treatment with light of awavelength from 200 to 600 nm.

[0014] The invention relates also to a composition comprising

[0015] (A) a coating system based on

[0016] (I) a polyacrylate polyol and/or polyester polyol with melamineor

[0017] (II) a polyacrylate polyol and/or polyester polyol with a blockedor unblocked polyisocyanate or

[0018] (III) a carboxyl-, anhydride- or amino-functional polyesterand/or polyacrylate with an epoxy-functional polyester or polyacrylate,or

[0019] (IV) a mixture of (I), (II), (III) and/or (IV),

[0020] (B) an OH—, NH₂—, COOH—, epoxy- or NCO-functional resincontaining, in addition, at least one ethylenically unsaturated doublebond, it being necessary for a spacer group of at least 4 linearlylinked atoms to be present between the double bond and the functionalgroup,

[0021] wherein components (A) and (B) do not contain halogen, and

[0022] (C) at least one photoinitiator.

[0023] Constituents of component (A) are, for example, surface-coatingor coating-system constituents that are customary in the art. In thecontext of the present invention, component (A) represents a surfacecoating or a coating.

[0024] Constituents of component (A) are, for example, polymers that arederived from α,β-unsaturated acids or from derivatives thereof. Examplesthereof are polyacrylates and polymethacrylates, polymethylmethacrylatesimpact-resistant modified with butyl acrylate, polyacrylamides andpolyacrylonitriles. Also of interest are, for example, siliconeacrylates. Further constituents of component (A) may be polyurethanesthat are derived on the one hand from polyethers, polyesters andpolyacrylates having free hydroxy groups and on the other hand fromaliphatic or aromatic polyisocyanates, and precursors thereof. Theconstituents of component (A) also include, for example, cross-linkableacrylic resins that are derived from substituted acrylic acid esters,for example epoxy acrylates, urethane acrylates or polyester acrylates.Furthermore, alkyl resins, polyester resins and acrylate resins, andmodifications thereof, that are cross-linked with melamine resins, urearesins, isocyanates, isocyanurates, polyisocyanates, polyisocyanuratesor epoxy resins may be a constituent of component (A).

[0025] Component (A) is, for example, generally a film-forming binderbased on a thermoplastic or thermocurable resin, predominantly on athermocurable resin. Examples thereof are alkyd, acrylic, polyester,phenol, melamine, epoxy and polyurethane resins and mixtures thereof.Examples thereof are described, for example, in Ullmann's Encyclopediaof Industrial Chemistry, 5th Ed., Vol. A18, pp. 368-426, VCH, Weinheim1991.

[0026] Component (A) may be a cold-curable or hot-curable binder, withthe addition of a curing catalyst possibly being advantageous. Suitablecatalysts that accelerate the full cure of the binder are described, forexample, in Ullmann's Encyclopedia of Industrial Chemistry, Vol. A18, p.469, VCH Verlagsgesellschaft, Weinheim 1991.

[0027] Examples of coatings (A) with specific binders are:

[0028] 1. surface coatings based on cold- or hot-cross-linkable alkyd,acrylate, polyester, epoxy or melamine resins or mixtures of suchresins, where appropriate with the addition of a curing catalyst;

[0029] 2. two-component polyurethane surface coatings based onhydroxy-group-containing acrylate, polyester or polyether resins andaliphatic or aromatic isocyanates, isocyanurates or polyisocyanates;

[0030] 3. one-component polyurethane surface coatings based on blockedisocyanates, isocyanurates or polyisocyanates that are de-blocked duringstoving; if desired, the addition of melamine resins is also possible;

[0031] 4. one-component polyurethane surface coatings based on aliphaticor aromatic urethanes or polyurethanes and hydroxy-group-containingacrylate, polyester or polyether resins;

[0032] 5. one-component polyurethane surface coatings based on aliphaticor aromatic urethane acrylates or polyurethane acrylates having freeamine groups in the urethane structure and melamine resins or polyetherresins, where appropriate with the addition of a curing catalyst;

[0033] 6. two-component surface coatings based on (poly)ketimines andaliphatic or aromatic isocyanates, isocyanurates or polyisocyanates;

[0034] 7. two-component surface coatings based on (poly)ketimines and anunsaturated acrylate resin or a polyacetoacetate resin or amethacrylamidoglycolate methyl ester;

[0035] 8. two-component surface coatings based on carboxyl-group- oramino-group-containing polyacrylates and polyepoxides;

[0036] 9. two-component surface coatings based onanhydride-group-containing acrylate resins and a polyhydroxy orpolyamino component;

[0037] 10. two-component surface coatings based on acrylate-containinganhydrides and polyepoxides;

[0038] 11. two-component surface coatings based on (poly)oxazolines andanhydride-group-containing acrylate resins or unsaturated acrylateresins or aliphatic or aromatic isocyanates, isocyanurates orpolyisocyanates;

[0039] 12. two-component surface coatings based on unsaturatedpolyacrylates and polymalonates;

[0040] 13. thermoplastic polyacrylate surface coatings based onthermoplastic acrylate resins or extrinsically cross-linking acrylateresins in combination with etherified melamine resins;

[0041] 14. surface-coating systems based on siloxane-modified acrylateresins.

[0042] Blocked isocyanates as may be used in component (A) aredescribed, for example, in Organischer Metallschutz: Entwicklung undAnwendung von Beschichtungsstoffen, pp. 159-160, Vincentz Verlag,Hannover (1993). Such compounds are those wherein the highly reactiveNCO group is ‘blocked’ by reaction with specific radicals, for example,primary alcohols, phenol, ethyl acetoacetate, ε-caprolactam,phthalimide, imidazole, oxime and amine. The blocked isocyanate isstable in liquid systems and also in the presence of hydroxy groups. Onheating, the blocking agents are removed again and the NCO group isfreed.

[0043] 1-component (1C) and 2-component (2C) systems are described, forexample, in Ullmann's Encyclopedia of Industrial Chemistry, Vol. A18,Paints and Coatings, pp. 404-407, VCH Verlagsgesellschaft mbH, Weinheim(1991).

[0044] It is possible to optimise the composition by specially adaptingthe formulation, for example by varying the binder/cross-linker ratio.The person skilled in the art of surface-coating technology will befamiliar with such measures.

[0045] In the curing process according to the invention the compositionis preferably a composition based on acrylate/melamine, 2-componentpolyurethane, 1-component polyurethane, 2-component epoxy or 1-componentepoxy/carboxy. Mixtures of those systems are also possible, for examplethe addition of melamine to 1-component polyurethanes.

[0046] Component (A) is preferably a binder based on a polyacrylate withmelamine. Preference is given also to a system based on a polyacrylatepolyol and/or polyester polyol with an unblocked polyisocyanate.

[0047] Component (B) consists essentially of monomeric and/or oligomericcompounds having ethylenically unsaturated bonds (pre-polymers) that, inaddition, contain at least one or more OH, NH₂, COOH, epoxy or NCOgroups capable of reacting with the binder and/or cross-linker ofcomponent (A). After application and thermal curing, the ethylenicallyunsaturated bonds are converted into a cross-linked,high-molecular-weight form by means of UV radiation. Examples ofcomponent (B) are described, for example, in the publication mentionedhereinbefore, Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed.,Vol. A18, pp. 451-453, or by S. Urano, K. Aoki, N. Tsuboniva and R.Mizuguchi in Progress in Organic Coatings, 20 (1992), 471-486, or by H.Terashima and O. Isozaki in JOCCA 1992 (6), 222. (B) may be, forexample, an OH-group-containing, unsaturated acrylate, for examplehydroxyethyl acrylate, hydroxybutyl acrylate or a glycidyl acrylate.Component (B) may have any desired structure (for example it may containunits of polyester, polyacrylate, polyether, etc.) provided that itincludes an ethylenically unsaturated double bond and also, in addition,free OH, COOH, NH₂, epoxy or NCO groups.

[0048] (B) may also be obtained, for example, by reacting anepoxy-functional oligomer with acrylic acid or methacrylic acid.

[0049] A typical example of an OH-functional oligomer having vinylicdouble bonds is

[0050] obtained by reaction of CH₂═CHCOOH with

[0051] A further possible method of preparing component (B) is, forexample, the reaction of an oligomer that contains only one epoxy groupand has a free OH group in another position in the molecule.

[0052] Also suitable as component (B) are, for example,siloxane-group-containing polymers that contain free OH groups and, inaddition, free double bonds. Those polymers can be obtained, forexample, by reacting an epoxy-functional polysiloxane with acrylic acidor methacrylic acid or derivatives thereof, for example

[0053]CH₂═CHCOO—CH₂CH(OH)CH₂O—(CH₂)_(m)—[Si(CH₃)₂—O]_(n)—Si(CH₃)₂—(CH₂)_(m)—OCH₂CH(OH)CH₂OC(O)CH═CH₂.Such products are available commercially.

[0054] Suitable spacer groups of at least 4 linearly linked atomspositioned between the double bond and the functional group in component(B) are, for example, the following structures: —(CH₂)_(y)—, whereiny≧4, or

[0055] wherein y≧2, or

[0056] wherein x=from 1 to 3 and y≧2. Preference is given to

[0057] The number of spacer atoms is at least 4, for example from 4 to16, 6-16, preferably from 4 to 12.

[0058] The compositions contain, for example, from 1 to 50%, e.g. from 5to 30%, especially from 10 to 25%, component (B), based on 100 parts ofcomponent (A).

[0059] According to the invention there may be used as photoinitiator(C) any known compound that is capable of initiating radicalpolymerisation when irradiated with light.

[0060] Examples thereof are:

[0061] benzophenone, benzophenone derivatives, acetophenone,acetophenone derivatives, for example 1-hydroxy-cyclohexyl-phenylketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-oneor 2-hydroxy-2-methyl-1-phenyl-propanone, dialkoxyacetophenones,α-hydroxy- or α-amino-acetophenones, for example(4-morpholino-benzoyl)-1-benzyl-1-dimethylamino-propane or(4-methylthiobenzoyl)-1-methyl-1-morpholino-ethane,4-aroyl-1,3-dioxolanes, benzoin alkyl ethers and benzil ketals, forexample 2,2-dimethoxy-1,2-diphenylethan-1-one, monoacylphosphine oxides,for example 2,4,6-trimethylbenzoyl-diphenylphosphine oxide,bisacylphosphine oxides, for examplebis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide,bis(2,4,6-trimethylbenzoyl)-(2-methylprop-1-yl)-phosphine oxide,bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide and trisacylphosphineoxides. In certain cases it may be advantageous to use mixtures of twoor more photoinitiators, for example mixtures ofbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide orbis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone orhydroxy-2-methyl-1-phenyl-propanone or2-methoxy-1-phenyl-ethane-1,2-dione.

[0062] Component (C) is preferably a compound of formula I

[0063] wherein

[0064] R₁ is hydrogen, C₁-C₁₈alkyl, C₁-C₁₈alkoxy, —OCH₂CH₂—OR₅, a group

[0065] or a group

[0066] wherein

[0067] I is an integer from 2 to 10 and

[0068] A is a radical

[0069] R₂ and R₃ are each independently of the other hydrogen,C₁-C₆alkyl, phenyl, C_(1-C) ₁₆alkoxy, OSiR₆R₇R₈ or—O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl wherein

[0070] q is an integer from 1 to 20, or

[0071] R₂ and R₃, together with the carbon atom to which they arebonded, form a cyclohexyl ring;

[0072] R₄ is hydroxy, C₁-C₁₆alkoxy or —O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl;

[0073] with the proviso that R₂, R₃ and R₄ are not all simultaneouslyC₁-C₁₆alkoxy or —O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl;

[0074] R₅ is hydrogen, C₁-C₈alkyl,

[0075] R₆, R₇ and R₈ are each independently of the others C₁-C₄alkyl orphenyl;

[0076] or a compound of formula (Ia)

[0077] wherein

[0078] R₉, R₁₀, R₁₁ and R₁₂ are each independently of the othershydrogen, methyl, phenyl, methoxy, —COOH, unsubstituted orC₁-C₄alkyl-substituted phenyl, or a group —OCH₂CH₂OR₅ or —SCH₂CH₂OR₅wherein

[0079] R₅ is as defined for formula I;

[0080] or a compound of formula (Ib)

[0081] wherein

[0082] R₁₃ is hydrogen, C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio, halogenor a group N(R₁₇)₂;

[0083] R₁₄ has one of the meanings indicated for R₁₃ or is the group

[0084] in which case the radical R₁₃ from formula Ib and the radical R₁₃from this group are together a direct bond and the other radicals are asdefined below;

[0085] R₁₅ is C₁-C₈alkyl;

[0086] R₁₆ is hydrogen, —CH═CHR₂₀, or phenyl that is unsubstituted ormono- to tri-substituted by C₁-C₁₂alkyl, C₁-C₄alkoxy or by halogen; or

[0087] R₁₅ and R₁₆, together with the carbon atom to which they arebonded, form a cyclohexyl ring;

[0088] R₁₇ and R₁₈ are each independently of the other C₁-C₄alkyl or

[0089] R₁₇ and R₁₈, together with the nitrogen atom to which they arebonded, form a five- or six-membered, saturated or unsaturated ring,which may be interrupted by —O—, —NH— or by —N(CH₃)—,

[0090] R₁₉ is hydrogen or C₁-C₁₂alkyl; and

[0091] R₂₀ is hydrogen or C₁-C₄-alkyl;

[0092] or a compound of formula II

[0093] wherein

[0094] R₂₁ is naphthyl, anthracyl, an O- or S-containing, 5- or6-membered heterocyclic ring or a group

[0095] R₂₂ is C₁-C₁₂alkyl, cyclohexyl, cyclopentyl, C₂-C₁₂alkenyl,phenyl-C₁-C₄alkyl; phenyl, biphenyl or naphthyl each of which isunsubstituted or mono- to tetra-substituted by C₁-C₄alkyl and/or byC₁-C₄alkoxy; C₂-C₁₈alkyl interrupted one or more times by —O—; orSi(R₂₈)(R₂₉)(R₃₀);

[0096] R₂₃, R₂₄, R₂₅, R₂₆ and R₂₇ are each independently of the othershydrogen, C₁-C₈alkyl, C₁-C₈alkoxy, C₁-C₈alkylthio, phenyloxy,phenylthio, phenyl that is unsubstituted or mono- to tetra-substitutedby C₁-C₄alkyl and/or by C₁-C₄alkoxy, phenyl-C₁-C₄alkyl, halogen or NO₂;

[0097] R₂₈, R₂₉ and R₃₀ are each independently of the others C₁-C₈alkyl,cyclohexyl, cyclopentyl, phenyl or C₁-C₈alkoxy;

[0098] or a compound of formula III

[0099] wherein

[0100] Z is S or O;

[0101] R₃₁ and R₃₂ are each independently of the other C₁-C₁₈alkyl,C₂-C₁₈alkyl interrupted one or more times by —O—, phenyl-substitutedC₁-C₄alkyl, C₂-C₄alkenyl; phenyl, naphthyl or biphenyl each of which isunsubstituted or mono- to penta-substituted by halogen, hydroxy,C₁-C₈alkyl and/or by C₁-C₈alkoxy; C₅-C₁₂cycloalkyl, an O-, S- orN-containing, 5- or 6-membered heterocyclic ring, or a group COR₃₃, or

[0102] R₃₁ is a radical

[0103] OH, OR₃₄, O⁻NH₄ ⁺ or O⁻[M^(n+)]_(1/n) wherein

[0104] n is an integer from 1 to 3 and

[0105] M is an n-valent metal ion, or

[0106] R₃₁ and R₃₂ together are C₄-C₇alkylene and form a ring togetherwith the P atom to which they are bonded;

[0107] R₃₃ is C₁-C₁₈alkyl, C₃-C₁₂cycloalkyl, C₂-C₁₈alkenyl; phenyl,naphthyl or biphenyl each of which is unsubstituted or mono- totetra-substituted by C₁-C₈alkyl, C₁-C₈alkoxy, C₁-C₈alkylthio and/or byhalogen; an O-, S- or N-containing, 5- or 6-membered heterocyclic ring,or a group

[0108] R₃₄ is C₁-C₈alkyl, phenyl, naphthyl, C₁-C₈alkylphenyl orC₁-C₄alkylnaphthyl;

[0109] Y is phenylene, C₁-C₁₂alkylene or C₅-C₆cycloalkylene;

[0110] X is C₁-C₁₈alkylene, C₂-C₁₈alkylene interrupted one or more timesby —O—, —S—, —NR₃₅—, P(O)R₃₆— or by —SO₂—, or C₁-C₆alkylene substitutedby Cl, F, C₁-C₄alkoxy, COOR₃₇, phenyl, phenyl-C₁-C₄alkyl,naphthyl-C₁-C₄alkyl, C₁-C₄alkylphenyl, C₁-C₄alkylnaphthyl,phenyl-C₁-C₄alkoxy, naphthyl-C₁-C₄alkoxy and/or by CN, or

[0111] X is C₁-C₈alkylene substituted by one or two radicals of formulaA

[0112] or

[0113] X is a group of formula A₁-A₉

[0114] wherein

[0115] a and b are each independently of the other 0 or 1, and the sumof d and f is an integer from 3 to 8, with the proviso that neither dnor f is 0, or

[0116] X is a group —CH₂—CH═CH—CH₂— or —CH₂—C≡C—CH₂, or

[0117] X is phenylene, xylylene,

[0118] each of which is unsubstituted or mono- to tri-substituted by Cl,F, C₁-C₄alkyl and/or by C₁-C₄alkoxy, or

[0119] X is phenylene that is substituted by one or two groups (A) andthat, in addition, may be mono- to tri-substituted by Cl, F, C₁-C₄alkyland/or by C₁-C₄alkoxy, or

[0120] X is a group of formula A₁₀-A₁₃

[0121] Q is a single bond, CR₃₉R₄₀, —O—, —S—, —NR₃₅—, —SO₂—, —(CH₂)_(p)—or —CH═CH—;

[0122] p is an integer from 2 to 12;

[0123] Z is O or S;

[0124] R₃₅ is hydrogen, C₁-C₁₂alkyl or phenyl;

[0125] R₃₆ is C₁-C₄alkyl or phenyl; and

[0126] R₃₇ is C₁-C₁₂alkyl, C₂-C₁₈alkyl interrupted one or more times by—O—, benzyl, phenyl, cyclopentyl or cyclohexyl;

[0127] R₃₈ is hydrogen, C₁-C₄alkyl, C₁-C₄alkoxy or halogen;

[0128] R₃₉ is hydrogen, methyl or ethyl; and

[0129] R₄₀ is hydrogen or C₁-C₄alkyl;

[0130] or component (C) is a mixture of a compound of formula I, Ia, Ibor II with a compound of formula III.

[0131] C₁-C₂₀Alkyl is linear or branched and is, for example, C₁-C₁₈—,C₁-C₁₂—, C₁-C₈—, C₁-C₆— or C₁-C₄-alkyl. Examples are methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl,hexyl, heptyl, 2,4,4-trimethyl-pentyl, 2-ethylhexyl, octyl, nonyl,decyl, undecyl, dodecyl, tetradecyl, heptadecyl, octadecyl and icosyl.C₁-C₁₈Alkyl, C₁-C₁₂alkyl, C₁-C₈alkyl and C₁-C₄alkyl are as definedhereinbefore up to the appropriate number of carbon atoms.

[0132] C₂-C₁₈Alkyl interrupted one or more times by —O— or by —S— isinterrupted, for example, by —O— from one to five times, e.g. from oneto three times or once or twice, resulting in, for example, structuralunits such as —S(CH₂)₂OH, —O(CH₂)₂OH, —O(CH₂)₂OCH₃, —O(CH₂CH₂O)₂CH₂CH₃,—CH₂—O—CH₃, —CH₂CH₂—O—CH₂CH₃, —[CH₂CH₂O]_(y)—CH₃ wherein y=from 1 to 5,—(CH₂CH₂O)₅CH₂CH₃, —CH₂—CH(CH₃)—O—CH₂—CH₂CH₃ and —CH₂—CH(CH₃)—O—CH₂—CH₃.

[0133] C₃-C₁₂Cycloalkyl is, for example, cyclopropyl, cyclopentyl,cyclohexyl, cyclooctyl or cyclododecyl. C₅-C₁₂Cycloalkyl is, forexample, cyclopentyl, cyclohexyl, cyclooctyl or cyclododecyl. Preferenceis given to cyclopentyl and cyclohexyl, especially cyclohexyl.

[0134] C₁-C₁₈Alkoxy is e.g. methoxy, ethoxy, n-propoxy, isopropoxy,n-butoxy, isobutoxy, sec-butoxy or tert-butoxy, pentyloxy, hexyloxy,heptyloxy, decyloxy or dodecyloxy, for example C₁-C₁₂alkoxy,C₁-C₈alkoxy, preferably C₁-C₄alkoxy, especially methoxy. C₁-C₈Alkoxy isas defined hereinbefore up to the appropriate number of carbon atoms.

[0135] C₁-C₁₂Alkythio is linear or branched and is e.g. methylthio,ethylthio, n-propylthio, iso-propylthio, n-butylthio, isobutylthio,sec-butylthio or tert-butylthio, pentylthio, hexylthio, heptylthio,decylthio or dodecylthio, for example C₁-C₈alkylthio, preferablyC₁-C₄alkylthio, especially methylthio.

[0136] An O- or S-containing, 5- or 6-membered heterocyclic ring is, forexample, furyl, thienyl, oxinyl or dioxinyl.

[0137] An O-, S- or N-containing, 5- or 6-membered heterocyclic ring is,for example, furyl, thienyl, pyrrolyl, pyridyl, oxinyl or dioxinyl.

[0138] C₂-C₁₂Alkenyl is, for example, allyl, methallyl,1,1-dimethylallyl, butenyl, hexenyl, octenyl or dodecenyl, for exampleC₂-C₈alkenyl or C₂-C₄alkenyl, especially allyl. C₂-C₄Alkenyl is, forexample, allyl, methallyl, 1,1-dimethylallyl or butenyl.

[0139] The radical —O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl represents from 1 to 20consecutive ethylene oxide units, the chain thereof being terminated bya C₁-C₁₆alkyl. q is preferably from 1 to 10, for example from 1 to 8,especially from 1 to 6. The chain of ethylene oxide units is terminatedpreferably by a C₁-C₁₀alkyl, for example by a C₁-C₈alkyl, especially bya C₁-C₄alkyl.

[0140] Phenyl-C₁-C₄alkyl is, for example, benzyl, phenylethyl,α-methylbenzyl or α,α-dimethylbenzyl, especially benzyl.

[0141] Substituted phenyl, naphthyl or biphenyl is mono- to penta-, forexample, mono- to tetra-, e.g. mono-, di- or tri-, especially di- ortri-substituted.

[0142] R₃₁, R₃₂ and R₃₃ as substituted phenyl, naphthyl or biphenyl aresubstituted, for example, by linear or branched C₁-C₈alkyl, such asmethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl or octyl, or by linear or branchedC₁-C₈-alkoxy, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy,isobutoxy, sec-butoxy, tert-butoxy, hexyloxy or octyloxy, or by linearor branched C₁-C₈alkylthio, such as methylthio, ethylthio, n-propylthio,isopropylthio, n-butylthio, isobutylthio, sec-butylthio, tert-butylthio,pentylthio or hexylthio, or by halogen, such as fluorine, chlorine,bromine or iodine. Preferred substituents of R₃₁, R₃₂ and R₃₃ as phenyl,naphthyl and biphenyl are C₁-C₄alkyl, especially methyl, C₁-C₄alkoxy,especially methoxy, and chlorine. R₃₁, R₃₂ and R₃₃ are especially, forexample, 2,4,6-trimethylphenyl, 2,6-dichlorophenyl, 2,6-dimethylphenylor 2,6-dimethoxyphenyl.

[0143] Examples of n-valent metals (n=from 1 to 3) are Na, Li, K, Mg,Ca, Ba, Fe, Co and Al.

[0144] When R₃₁ and R₃₂ are C₄-C₇alkylene and, together with the P atomto which they are bonded, form a ring, that ring (including the P atom)is preferably five- or six-membered.

[0145] C₁-C₈Alkylphenyl is, for example; C₁-C₄alkylphenyl, for exampletolyl, xylyl, mesityl, ethyl-phenyl or diethylphenyl, preferably tolylor mesityl.

[0146] C₁-C₄Alkylnaphthyl is naphthyl substituted by methyl, ethyland/or propyl or butyl.

[0147] C₁-C₁₈alkylene and C₁-C₁₂alkylene are linear or branchedalkylene, for example methylene, ethylene, propylene, isopropylene,n-butylene, sec-butylene, isobutylene, tert-butylene, pentylene,hexylene, heptylene, octylene, nonylene, decylene, dodecylene,tetradecylene, heptadecylene or octadecylene. X and Y are eachespecially C₁-C₁₂alkylene, for example ethylene, decylene, —CH(C₁₁H₂₃)—,—CH(CH₃)—CH₂—, —CH(CH₃)—(CH₂)₂—, —CH(CH₃)—(CH₂)₃—, —C(CH₃)₂—CH₂— or

[0148] When X is C₂-C₁₈alkylene interrupted by —O—, —S—, —NR₃₅—,—P(O)R₃₆— or by —SO₂—, there are obtained, for example, structural unitssuch as —CH₂—O—CH₂—, —CH₂CH₂—O—CH₂CH₂—, —[CH₂CH₂O]_(y)— wherein y=from 1to 9, —(CH₂CH₂O)₇CH₂CH₂—, —CH₂—CH(CH₃)—O—CH₂—CH(CH₃)—, —CH₂—S—CH₂—,—CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂CH₂—S—CH₂CH₂CH₂—, —(CH₂)₃—S—(CH₂)₃—S—(CH₂)₃—,—CH₂—(NR₃₅)—CH₂—, —CH₂CH₂—(NR₃₅)—CH₂CH₂—, —CH₂—(P(O)R₃₆)—CH₂—,—CH₂CH₂—(P(O)R₃₆)—CH₂CH₂—,

[0149] —CH₂)₂—SO₂—CH₂— and —CH₂CH₂—SO₂—CH₂CH₂—.

[0150] C₁-C₄Alkoxy substituents are, for example, methoxy, ethoxy,propoxy and butoxy, especially methoxy. C₁-C₆alkylene substituted byC₁-C₄alkoxy or by —COOR₃₇ is, for example, —CH(OCH₃)— or—CH(COOCH₃)—CH₂—.

[0151] C₁-C₄Alkylphenyl is, for example, tolyl, xylyl, mesityl,ethylphenyl or diethylphenyl, preferably tolyl or mesityl.

[0152] C₁-C₄Alkylnaphthyl is naphthyl substituted by methyl, ethyland/or propyl or butyl. Phenyl-C₁-C₄alkyl is, for example, benzyl,phenylethyl, α-methylbenzyl or α,α-dimethylbenzyl, especially benzyl.

[0153] Naphthyl-C₁-C₄alkyl is, for example, naphthylmethyl,naphthylethyl, naphthyl-(1-methyl)-eth-1-yl ornaphthyl-(1,1-dimethyl)eth-1-yl, especially naphthylmethyl.

[0154] Phenyl-C₁-C₄alkoxy is to be understood as being, for example,benzyloxy, phenylethyloxy, α-methylbenzyloxy or α,α-dimethylbenzyloxy,especially benzyloxy.

[0155] Naphthyl-C₁-C₄alkoxy is, for example, naphthylmethyloxy ornaphthylethyloxy.

[0156] Examples of groups of formula (A₁) wherein the sum of d and f isfrom 3 to 8 are:

[0157] Examples of groups of formulae A₂, A₃, A₄, A₅, A₆, A₇, A₈ and A₉are

[0158] Examples of groups of formula A₁₀ are

[0159] Examples of unsubstituted and substituted phenylene and xylyleneare

[0160] The preparation of compounds of formulae I and Ia is generallyknown and some of the compounds are available commercially. Thepreparation of oligomeric compounds of formula I is described, forexample, in EP-A-161 463. A description of the preparation of compoundsof formula Ia may be found, for example, in EP-A-209 831.

[0161] The preparation of compounds of formula Ib is described, forexample, in EP-A-284 561. The compounds of formula III are prepared, forexample, in the manner disclosed in EP-A-184 095.

[0162] Some compounds of formulae Ib, II and III are also availablecommercially.

[0163] Preference is given to compounds of formula I wherein R₁ ishydrogen, C₁-C₁₂alkyl or —OCH₂CH₂—OR₅; R₂ and R₃ are each independentlyof the other C₁-C₆alkyl, phenyl or C₁-C₁₆alkoxy or R₂ and R₃, togetherwith the carbon atom to which they are bonded, form a cyclohexyl ring;R₄ is hydroxy or C₁-C₁₆alkoxy; R₅ is hydrogen or

[0164] and to compounds of formula (Ia) wherein R₉, R₁₀, R₁₁ and R₁₂ arehydrogen; and to compounds of formula (Ib) wherein R₁₃ is hydrogen; R₁₄is C₁-C₄alkylthio or N(R₁₇R₁₈); R₁₅ is C₁-C₈alkyl; R₁₆ is phenyl; R₁₇and R₁₈ are each independently of the other C₁-C₄alkyl or R₁₇ and R₁₈,together with the nitrogen atom to which they are bonded, form asaturated six-membered ring, which may be interrupted by —O—; and tocompounds of formula II wherein R₂₁ is phenyl and R₂₂ is C₁-C₁₂alkyl;and to compounds of formula III wherein Z is O; R₃₁ and R₃₂ are eachindependently of the other C₁-C₁₈alkyl; phenyl that is unsubstituted ormono- to penta-substituted by C₁-C₈alkyl and/or by C₁-C₈-alkoxy; or agroup COR₃₃; and R₃₃ is phenyl that is unsubstituted or mono- totetra-substituted by C₁-C₈alkyl or by C₁-C₈alkoxy.

[0165] Preferably, R₂ and R₃ in formula I are each independently of theother C₁-C₆alkyl or, together with the carbon atom to which they arebonded, form a cyclohexyl ring, and R₄ is hydroxy.

[0166] More especially, R₂ and R₃ in formula I are identical and areeach methyl, and R₄ is hydroxy or isopropoxy.

[0167] In formula Ia R₉-R₁₂ are preferably hydrogen.

[0168] Preferably, R₁₆ in formula Ib is phenyl or —CH═CHR₂₀, R₁₄ isC₁-C₄alkylthio or N(R₁₇)₂, and R₁₅, R₁₇ and R₁₈ are C₁-C₄alkyl.

[0169] In formula II R₂₁ is preferably phenyl and R₂₂ is C₁-C₄alkyl.

[0170] Preferably, R₃₁ in formula III is COR₃₃ wherein R₃₃ is phenylmono- to tetra-substituted by C₁-C₄alkyl, C₁-C₄alkoxy and/or by halogen,and R₃₂ is C₁-C₁₂alkyl, unsubstituted phenyl or phenyl mono- topenta-substituted by C₁-C₄alkyl and/or by C₁-C₄alkoxy.

[0171] Furthermore, in formula III preferably R₃₁ and R₃₂ are phenyl andR₃₃ is phenyl mono- to tri-substituted by C₁-C₄alkyl and/or byC₁-C₄alkoxy.

[0172] Z is preferably O.

[0173] As component (C) special preference is given to1-hydroxy-cyclohexyl-phenyl ketone,1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one or2-hydroxy-2-methyl-1-phenyl-propanone,(4-morpholino-benzoyl)-1-benzyl-1-dimethylamino-propane or(4-methylthiobenzoyl)-1-methyl-1-morpholino-ethane,2,2-dimethoxy-1,2-diphenylethan-1-one,2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide,bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentylphosphine oxide,bis(2,4,6-trimethylbenzoyl)-(2-methylprop-1-yl)-phosphine oxide,bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide, and mixtures ofbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone, hydroxy-2-methyl-1-phenyl-propanoneor 2-methoxy-1-phenyl-ethane-1,2-dione; or ofbis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone, hydroxy-2-methyl-1-phenyl-propanoneor 2-methoxy-1-phenyl-ethane-1 ,2-dione; or of2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone, hydroxy-2-methyl-1-phenyl-propanoneor 2-methoxy-1-phenyl-ethane-1,2-dione.

[0174] The photopolymerisable compositions contain the photoinitiator(C) advantageously in an amount from 0.05 to 20% by weight, preferablyfrom 2 to 10% by weight, based on 100 parts of component (A).

[0175] When the photoinitiator (C) is a mixture of a compound of formulaI, Ia, Ib or II with a compound of formula III, the proportion of thecompound(s) of formula I, Ia, Ib or II in the mixture is, for example,from 25 to 90%, e.g. from 25 to 75%, preferably from 50 to 75%.

[0176] Preference is given to a composition comprising (A) polyesterpolyol, acrylate polyol or hexamethoxymethyrmelamine and (B)isocyanurate or OH-functionalised acrylate and (C)1-hydroxy-cyclohexyl-phenyl ketone or 25%bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 75%1-hydroxy-cyclohexyl-phenyl ketone or4-[(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methyl-ethane.

[0177] It is characteristic of the composition that it comprises an OH—,NH₂—, COOH—, epoxy- or NCO-functionalised component that also, inaddition, contains free double bonds separated from the functional groupby a spacer group of at least 4 linearly linked atoms (B), and aphotoinitiator (C). In accordance with the process according to theinvention, the addition of those components allows a furthercross-linking of the surface coating on irradiation with light after thethermal curing, resulting in a surface coating having improved surfaceproperties, especially in respect of the hardness and resistance toscratching.

[0178] The surface coatings according to the invention may comprise anorganic solvent or solvent mixture in which the binder and/or thecross-linker is (are) soluble or dispersible. The composition may,however, also be an aqueous solution or dispersion. It is also possible,for example, for one of the two components to serve as the dispersionmedium or dissolution medium for the other component. The vehicle mayalso be a mixture of an organic solvent and water. The coating may alsobe a high-solids surface coating or may be solvent-free (for example,powder coating composition).

[0179] The compositions according to the invention are prepared bymixing all the components. It is also possible, for example, first tolink only the OH—, NH₂—, COOH—, epoxy- or NCO-functionalised component(B) with component (A), or with a constituent thereof, via thefunctional group in question, and thereafter to mix in all the otherconstituents.

[0180] The compositions according to the invention may be applied to anydesired substrates, for example to metal, wood, plastics or ceramicmaterials. They are preferably used as finishing lacquers for thesurface-coating of motor vehicles. When the finishing lacquer consistsof two layers the lower layer of which is pigmented and the upper layerof which is not pigmented, the coating according to the invention may beused for the upper or the lower layer or for both layers, but preferablyfor the upper layer.

[0181] The compositions according to the invention may be applied to thesubstrates in accordance with the customary procedures, for example bypainting, spraying, pouring, immersion or electrophoresis; see alsoUllmann's Encyclopedia of Industrial Chemistry, 5th Ed., Vol. A18, pp.491-500.

[0182] The invention therefore relates also to a process for the coatingof a substrate wherein a composition according to the invention isapplied to the surface of the substrate, cured by means of heating andthen irradiated with UV light.

[0183] In addition to the photoinitiator the compositions may comprisefurther customary additives, or it is possible to add further additivesto the formulation in the process according to the invention.

[0184] For example, the composition may comprise further components inaddition to components (A), (B) and (C), or in the process according tothe invention it is possible to add to components (B) and (C) furtheradditives, for example light stabilisers, solvents, pigments, dyes,plasticisers, stabilisers, thixotropic agents, drying catalysts and/orflow improvers. Possible components are, for example, such as aredescribed in Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed.,Vol. A18, pp. 429-471, VCH, Weinheim 1991.

[0185] UV-absorbers, for example those of thehydroxyphenyl-benzotriazole, hydroxyphenyl-benzophenone, oxalic acidamide or hydroxyphenyl-s-triazine type, may be added as lightstabilisers. There may be used, for example, individual compounds ormixtures of those compounds with or without the use of stericallyhindered amines (HALS).

[0186] Possible drying catalysts, or curing catalysts, are, for example,organic metal compounds, amines, amino-group-containing resins and/orphosphines. Organic metal compounds are, for example, metalcarboxylates, especially those of the metals Pb, Mn, Co, Zn, Zr and Cu,and metal chelates, especially those of the metals Al, Ti and Zr, andorganometal compounds, for example organotin compounds.

[0187] Examples of metal carboxylates are the stearates of Pb, Mn andZn, the octanoates of Co, Zn and Cu, the naphthenates of Mn and Co andthe corresponding linoleates, resinates and tallates.

[0188] Examples of metal chelates are the aluminium, titanium andzirconium chelates of acetyl-acetone, ethyl acetoacetate,salicylaldehyde, salicylaldoxime, o-hydroxyacetophenone andethyltrifluoroacetoacetate and the alcoholates of those metals.

[0189] Examples of organotin compounds are dibutyltin oxide, dibutyltindilaurate and dibutyltin dioctanoate.

[0190] Examples of amines are especially tertiary amines, for exampletributylamine, triethanol-amine, N-methyl-diethanolamine,N-dimethylethanolamine, N-ethylmorpholine, N-methyl-morpholine anddiazabicyclooctane (triethylenediamine) and salts thereof. Furtherexamples are quaternary ammonium salts, for exampletrimethylbenzylammonium chloride. Amino-group-containing resins actsimultaneously as binder and curing catalyst. Amino-group-containingacrylate copolymers are examples thereof.

[0191] As curing catalyst there may also be used phosphines, for exampletriphenyl-phosphine. The pigments may be inorganic, organic or metallicpigments. Preferably, the coatings according to the invention contain nopigments and are used as clear lacquer.

[0192] Preference is given to the use of the composition according tothe invention as a coating, especially as a finishing lacquer for use inthe furniture industry and automobile industry, more especially as apigmented or non-pigmented top layer of the surface coating. The usethereof for underlying layers is, however, also possible.

[0193] When the composition according to the invention is used in theunderlying layer, with the simultaneous use of a UV-curable finishinglacquer, the adhesion of the UV-curable finishing lacquer to theunderlying layer is improved as a result of the reaction of the doublebonds present in each of the layers.

[0194] Preference is given to non-pigmented compositions and to a curingprocess without the addition of pigments.

[0195] The curing of the compositions according to the invention iscarried out thermally at first. The surface is after-cured by subsequentirradiation with UV light.

[0196] Accordingly, in the curing process according to the invention,the coating to be cross-linked is first of all cured by the action ofheat and the surface hardness is improved by the subsequent irradiationwith UV light.

[0197] The thermal curing is carried out generally in an oven, forexample a circulating-air oven, or by means of irradiation with IRlamps. Curing at room temperature without aids is likewise possible,depending on the binder system used. The curing temperatures aregenerally from room temperature to 150° C., for example from 25 to 150°C. or from 50 to 150° C. In the case of powder coating compositions, thecuring temperatures may be even higher, for example up to 250° C.

[0198] The photochemical curing step is carried out usually using lightof wavelengths from about 200 nm to about 600 nm, especially from 200 to450 nm. As light sources there are used a large number of the mostvaried types. Both point sources and planiform projectors (lamp carpets)are suitable. Examples are: carbon arc lamps, xenon arc lamps, medium-,high- and low-pressure mercury lamps, optionally doped with metalhalides (metal halide lamps), microwave-excited metal-vapour lamps,excimer lamps, superactinic fluorescent tubes, fluorescent lamps, argonfilament lamps, electronic flash lamps, photographic flood lights,electron beams and X-rays generated by means of synchrotrons or laserplasma. The distance between the lamp and the substrate according to theinvention to be irradiated may vary, for example, from 2 cm to 150 cm,according to the intended use and the type and strength of the lamp.Laser-light sources, for example excimer lasers, are especiallysuitable. The selection of the type of lamp is dependent especially onthe type of photoinitiator (C) used. For example, bisacyiphosphine oxidephotoinitiators are excited even by lamps having an emission spectrum ofrelatively long wavelength.

[0199] The Examples that follow illustrate the invention further. Unlessstated otherwise, parts or percentages relate, as they do in the rest ofthe description and in the patent claims, to weight.

EXAMPLES 1-4

[0200] A 2-component polyurethane clear lacquer is prepared by mixing:

[0201] 50.10 parts of Desmophen® 680; polyester polyol; 70% in butylacetate (Bayer AG)

[0202] 0.48 part of Baysilone® OL 17; flow improver; 10% in xylene(Bayer AG)

[0203] 1.45 parts of diazabicyclooctane (DABCO); accelerator; 10% inbutyl acetate

[0204] 14.64 parts of xylene/butyl acetate/Solvesso® 100 (2/2/1);(Solvesso®=aromatic hydrocarbons (Esso))

[0205] 14.76 parts of Desmodur® N 3390; isocyanurate; 90% (Bayer AG)

[0206] 18.57 parts of xylene/butyl acetate/Solvesso® 100 (2/2/1)

[0207] 100.00 parts of resin solid

[0208] To a sample of the lacquer thus prepared there are added 10%, andto a further sample 15%, (based on the resin solid) Ebecryl® 600,OH-functional acrylate resin (UCB) and 5% photoinitiator (PI-1 or PI-2);the mixture is applied to a white coil-coating sheet, air-dried for 15minutes and stoved at 80° C. for 30 minutes. A dry film thickness ofapproximately 40 μM is obtained.

[0209] 10 minutes after the thermal curing, the pendulum hardnessaccording to König (DIN 53157) is determined. Irradiation is thencarried out using a UV-processor (2×120 W/cm) at a band speed of 10m/min and the pendulum hardness is determined again. The higher thevalues of the pendulum hardness measurement, the more durable and harderis the cured surface.

[0210] The initiators used and the results of the pendulum hardnessmeasurements can be found in Table 1 below. TABLE 1 Pendulum hardness[sec] Ex- OH-function- Photo- before after ample al resin initiatorirradiation irradiation increase 1 10% Pl-1 29 41 12 2 10% Pl-2 34 47 133 15% Pl-1 31 46 15 4 15% Pl-2 34 53 19

EXAMPLE 5

[0211] A high-solids clear lacquer is prepared by mixing:

[0212] 56.16 g of Joncryl® 510; OH-functional acrylate; 80% in xylene(SC Johnson Polymer BV/Holland)

[0213] 19.18 g of Cymel® 303; hexamethoxymethylmelamine (CytecIndustries/USA)

[0214] 14.16 g of butanol

[0215] 9.89 g of methylamyl ketone (MAK)

[0216] 0.61 g of DC-57; flow improver; 10% in MAK (DOW Corning/Belgium)

[0217] 100.00 g

[0218] 0.5% p-toluenesulfonic acid (10% in butanol) is added to thatmixture. To a sample of the lacquer thus prepared there are added 15%8-hydroxyoctyl acrylate (HOAc) and to another sample 15% Tegomer® V-Si2150 (α,ω-acryloxyorgano-functional polydimethylsiloxane, GoldschmidtAG/Germany), and to each of two further samples there are added, inaddition, 6% 4-[(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methyl-ethane(Irgacure® 2959, Ciba Spezialitätenchemie/Switzerland) which has beendissolved beforehand in methyl ethyl ketone. The samples are eachapplied to a white coil-coating sheet, air-dried for 15 minutes andstoved at 120° C. for 30 minutes. A dry film thickness of approximately45 μm is obtained.

[0219] After the thermal curing, the sample sheets are cooled to 50° C.and irradiated using a UV-processor (2×81 W/cm) at a band speed of 5m/min. The pendulum hardness according to König (DIN 53157) isdetermined before and after irradiation.

[0220] The results of the pendulum hardness measurements are shown inTable 2. TABLE 2 Photoinitiator Pendulum hardness [sec] Resin beforeirradiation after irradiation Increase Without photoinitiator 57 64  7HOAc Without photoinitiator 59 57 −2 Tegomer With photoinitiator 53 9542 HOAc With photoinitiator 95 113  18 Tegomer

[0221] A clear increase in the pendulum hardness is observed in the caseof the samples to which photoinitiator has been added.

EXAMPLE 6

[0222] A high-solids clear lacquer is prepared by mixing:

[0223] 53.4 g of Joncryl® 510; OH-functional acrylate; 80% in xylene (SCJohnson Polymer BV/Holland)

[0224] 19.18 g of Cymel® 303; hexamethoxymethylmelamine (CytecIndustries/USA)

[0225] 14.16 g of butanol

[0226] 12.65 g of methylamyl ketone (MAK)

[0227] 0.61 g of DC-57; flow improver; 10% in MAK (DOW Corning/Belgium)

[0228] 100.00 g

[0229] 0.5% p-toluenesulfonic acid (10% in butanol) is added to thatmixture. To a sample of the lacquer thus prepared there are added 15%8-hydroxyoctyl acrylate (HOAc) and to another sample 15% Tegomer® V-Si2150 (α,ω-acryloxyorgano-functional polydimethylsiloxane, GoldschmidtAG/Germany), and to each of two further samples there are added, inaddition, 6% 4-[(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methyl-ethane(Irgacure® 2959, Ciba Spezialitatenchemie/Switzerland) which has beendissolved beforehand in methyl ethyl ketone. The samples are eachapplied to a white coil-coating sheet, air-dried for 15 minutes andstoved at 120° C. for 30 minutes. A dry film thickness of approximately45 μm is obtained.

[0230] After the thermal curing, the sample sheets are cooled to 50° C.and irradiated using a UV-processor (2×81 W/cm) at a band speed of 5m/min. The pendulum hardness according to König (DIN 53157) isdetermined before and after irradiation. The results of the pendulumhardness measurements are listed in Table 3. TABLE 3 PhotoinitiatorPendulum hardness [sec] Resin before irradiation after irradiationIncrease Without photoinitiator 53 57  4 HOAc Without photoinitiator 6980 11 Tegomer With photoinitiator 69 102  43 HOAc With photoinitiator 6395 32 Tegomer

EXAMPLE 7

[0231] To a sample of a 2C polyurethane lacquer mixture, as described inExample 1, there are added 15% 8-hydroxyoctyl acrylate (HOAc) and toanother sample 15% 4-hydroxybutyl acrylate (HBAc), and to each of twofurther samples there are added, in addition, 6%4-[(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methyl-ethane (Irgacure® 2959,Ciba Spezialitäten-chemie/Switzerland) which has been dissolvedbeforehand in methyl ethyl ketone. The samples are each applied to awhite coil-coating sheet, air-dried for 15 minutes and stoved at 80° C.for 30 minutes. A dry film thickness of approximately 45 μm is obtained.After the thermal curing, the sample sheets are cooled to 50° C. andirradiated using a UV-processor (2×81 W/cm) at a band speed of 5 m/min.The MEK-resistance is determined before and after irradiation. For thatpurpose, a piece of felt soaked with methyl ethyl ketone is laid on thelacquer surface and covered with a watch glass; the time until blisterformation is measured. The longer the time period until blisterformation, the more resistant is the surface-coating formulation. Theresults can be found in Table 4. TABLE 4 Photoinitiator MEK-resistance[min] Resin before irradiation after irradiation Increase Withoutphotoinitiator 2  2  0 HOAc Without photoinitiator 2  2  0 HBAc Withphotoinitiator 2 25 23 HOAc With photoinitiator 2 15 13 HBAc

[0232] The improvement in the resistance to solvent when aphotoinitiator has been added for the subsequent irradiation is clearlydiscernible.

EXAMPLE 8

[0233] A 2C polyurethane lacquer is prepared by mixing:

[0234] 54.80 g of Macrynal® SM 510N; acrylate polyol (Hoechst/Germany)

[0235] 0.15 g of Byk® 300; flow improver (Byk-Chemie/Germany)

[0236] 0.07 g of Nuodex zinc octanoate; accelerator

[0237] 11.50 g of butyl glycol acetate

[0238] 4.70 g of Solvesso 100; aromatic hydrocarbons (Esso)

[0239] 5.68 g of methyl isobutyl ketone (MIBK)

[0240] 23.10 g of Desmodur® N75; isocyanate (Bayer AG/Germany)

[0241] 100.00 g

[0242] To a sample of the lacquer thus prepared there are added 15%8-hydroxyoctyl acrylate (HOAC) and to a further sample there are added,in addition, 6% 4-[(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methyl-ethane(Irgacure® 2959, Ciba Spezialitatenchemie/Switzerland) which has beendissolved beforehand in methyl ethyl ketone. The samples are eachapplied to a white coil-coating sheet, air-dried for 15 minutes andstoved at 130° C. for 30 minutes. A dry film thickness of approximately45 μm is obtained.

[0243] After the thermal curing, the sample sheets are cooled to 50° C.and irradiated using a UV-processor (2×81 W/cm) at a band speed of 5m/min. The pendulum hardness according to König (DIN 53157) isdetermined before and after irradiation. The results of the pendulumhardness measurements are reproduced in Table 5. TABLE 5 PhotoinitiatorPendulum hardness [sec] Resin before irradiation after irradiationIncrease Without photoinitiator 118 120  2 HOAc With photoinitiator 120140 20 HOAc

What is claimed is:
 1. A process for the curing of a polymerisablecomposition comprising (A) a coating system based on (I) a polyacrylatepolyol and/or polyester polyol with melamine or (II) a polyacrylatepolyol and/or polyester polyol with a blocked or unblockedpolyisocyanate or (III) a carboxyl-, anhydride- or amino-functionalpolyester and/or polyacrylate with an epoxy-functional polyester orpolyacrylate, or (IV) a mixture of (I), (II), (Ill) and/or (IV), (B) anOH—, NH₂—, COOH—, epoxy- or NCO-functional resin containing, inaddition, at least one ethylenically unsaturated double bond, it beingnecessary for a spacer group of at least 4 linearly linked atoms to bepresent between the double bond and the functional group, whereincomponents (A) and (B) do not contain halogen, and (C) at least onephotoinitiator, by thermal treatment and, for the purpose of improvingthe surface properties, subsequent photochemical treatment with light ofa wavelength from 200 to 600 nm.
 2. A process according to claim 1wherein in the composition the photoinitiator (C) is a compound offormula I

wherein R₁ is hydrogen, C₁-C₁₈alkyl, C₁-C₁₈alkoxy, —OCH₂CH₂—OR₅, a group

or a group

wherein I is an integer from 2 to 10 and A is a radical

R₂ and R₃ are each independently of the other hydrogen, C₁-C₆alkyl,phenyl, C₁-C₁₆alkoxy, OSiR₆R₇R₈ or —O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl wherein qis an integer from 1 to 20, or R₂ and R₃, together with the carbon atomto which they are bonded, form a cyclohexyl ring; R₄ is hydroxy,C₁-C₁₆alkoxy or —O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl; with the proviso that R₂,R₃ and R₄ are not all simultaneously C₁-C₁₆alkoxy or—O(CH₂CH₂O)_(q)—C₁-C₁₆alkyl; R₅ is hydrogen, C₁-C₈alkyl,

R₆, R₇ and R₈ are each independently of the others C₁-C₄alkyl or phenyl;or a compound of formula (Ia)

wherein R₉, R₁₀, R₁₁ and R₁₂ are each independently of the othershydrogen, methyl, phenyl, methoxy, —COOH, unsubstituted orC₁-C₄alkyl-substituted phenyl, or a group —OCH₂CH₂OR₅ or —SCH₂CH₂OR₅wherein R₅ is as defined for formula I; or a compound of formula (Ib)

wherein R₁₃ is hydrogen, C₁-C₄alkyl, C₁-C₄alkoxy, C₁-C₄alkylthio,halogen or a group N(R₁₇R₁₈); R₁₄ has one of the meanings indicated forR₁₃ or is the group

in which case the radical R₁₃ from formula Ib and the radical R₁₃ fromthis group are together a direct bond and the other radicals are asdefined below; R₁₅ is C₁-C₈alkyl; R₁₆ is hydrogen, —CH═CHR₂₀, or phenylthat is unsubstituted or mono- to tri-substituted by C₁-C₁₂alkyl,C₁-C₄alkoxy or by halogen; or R₁₅ and R₁₆, together with the carbon atomto which they are bonded, form a cyclohexyl ring; R₁₇ and R₁₈ are eachindependently of the other C₁-C₄alkyl or R₁₇ and R₁₈, together with thenitrogen atom to which they are bonded, form a five- or six-membered,saturated or unsaturated ring, which may be interrupted by —O—, —NH— orby —N(CH₃)—, R₁₉ is hydrogen or C₁-C₁₂alkyl; and R₂₀ is hydrogen orC₁-C₄alkyl; or a compound of formula II

R₂₁ is naphthyl, anthracyl, an O- or S-containing, 5- or 6-memberedheterocyclic ring or a group

R₂₂ is C₁-C₁₂alkyl, cyclohexyl, cyclopentyl, C₂-C₁₂alkenyl,phenyl-C₁-C₄alkyl; phenyl, biphenyl or naphthyl each of which isunsubstituted or mono- to tetra-substituted by C₁-C₄alkyl and/or byC₁-C₄alkoxy; C₂-C₁₈alkyl interrupted one or more times by —O—; orSi(R₂₈)(R₂₉)(R₃₀); R₂₃, R₂₄, R₂₅, R₂₆ and R₂₇ are each independently ofthe others hydrogen, C₁-C₈alkyl, C₁-C₈alkoxy, C₁-C₈alkylthio, phenyloxy,phenylthio, phenyl that is unsubstituted or mono- to tetra-substitutedby C₁-C₄alkyl and/or by C₁-C₄alkoxy, phenyl-C₁-C₄alkyl, halogen or NO₂;R₂₈, R₂₉ and R₃₀ are each independently of the others C₁-C₈alkyl,cyclohexyl, cyclopentyl, phenyl or C₁-C₈alkoxy; or a compound of formulaIII

Z is S or O; R₃₁ and R₃₂ are each independently of the otherC₁-C₁₈alkyl, C₂-C₁₈alkyl interrupted one or more times by —O—,phenyl-substituted C₁-C₄alkyl, C₂-C₄alkenyl; phenyl, naphthyl orbiphenyl each of which is unsubstituted or mono- to penta-substituted byhalogen, hydroxy, C₁-C₈alkyl and/or by C₁-C₈alkoxy; C₅-C₁₂cycloalkyl, anO-, S- or N-containing, 5- or 6-membered heterocyclic ring, or a groupCOR₃₃, or R₃₁ is a radical

OH, OR₃₄, O⁻NH₄ ⁺ or O⁻[M^(n+)]_(1/n), wherein n is an integer from 1 to3 and M is an n-valent metal ion, or R₃₁ and R₃₂ together areC₄-C₇alkylene and form a ring together with the P atom to which they arebonded; R₃₃ is C₁-C₁₈alkyl, C₃-C₁₈cycloalkyl, C₂-C,₈alkenyl; phenyl,naphthyl or biphenyl each of which is unsubstituted or mono- totetra-substituted by C₁-C₈alkyl, C₁-C₈alkoxy, C₁-C₈alkylthio and/or byhalogen; an O-, S- or N-containing 5- or 6-membered hetero-cyclic ring,or a group

R₃₄ is C₁-C₈alkyl, phenyl, naphthyl, C₁-C₈alkylphenyl orC₁-C₄alkylnaphthyl; Y is phenylene, C₁-C₁₂alkylene orC₅-C₆cycloalkylene; X is C₁-C₁₈alkylene, C₂-C₁₈alkylene interrupted oneor more times by —O—, —S—, —NR₃₅—, P(O)R₃₆— or by —SO₂—, orC₁-C₆alkylene substituted by Cl, F, C₁-C₄alkoxy, COOR₃₇, phenyl,phenyl-C₁-C₄alkyl, naphthyl-C₁-C₄alkyl, C₁-C₄alkylphenyl,C₁-C₄alkylnaphthyl, phenyl-C₁-C₄alkoxy, naphthyl-C₁-C₄alkoxy and/or byCN, or X is C₁-C₈alkylene substituted by one or two radicals of formulaA

X is a group of formula A₁-A₉

a and b are each independently of the other 0 or 1, and the sum of d andf is an integer from 3 to 8, with the proviso that neither d nor f is 0,or X is a group —CH₂—CH═CH—CH₂— or —CH₂—C═C—CH₂—, or X is phenylene,xylylene

each of which is unsubstituted or mono- to tri-substituted by Cl, F,C₁-C₄alkyl and/or by C₁-C₄alkoxy, or X is phenylene that is substitutedby one or two groups (A) and that, in addition, may be mono- totri-substituted by Cl, F, C₁-C₄alkyl and/or by C₁-C₄alkoxy, or p1 X is agroup of formula A₁₀-A₁₃

Q is a single bond, CR₃₉R₄₀, —O—, —S—, —NR₃₅—, —SO₂—, —(CH₂)_(p)— or—CH═CH—; p is an integer from 2 to 12; Z is O or S; R₃₅ is hydrogen,C₁-C₁₂alkyl or phenyl; R₃₆ is C₁-C₄alkyl or phenyl; and R₃₇ isC₁-C₁₂alkyl, C₂-C₁₈alkyl interrupted one or more times by -O-, benzyl,phenyl, cyclopentyl or cyclohexyl; R₃₈ is hydrogen, C₁-C₄alkyl,C₁-C₄alkoxy or halogen; R₃₉ is hydrogen, methyl or ethyl; and R₄₀ ishydrogen or C₁-C₄alkyl; or a mixture of a compound of formula I, Ia, Ibor II with a compound of formula III.
 3. A process according to claim 1wherein in the composition in formula I R₁ is hydrogen, C₁-C₁₂alkyl or—OCH₂CH₂—OR₅; R₂ and R₃ are each independently of the other C₁-C₆alkyl,phenyl or C₁-C₁₆alkoxy or R₂ and R₃, together with the carbon atom towhich they are bonded, form a cyclohexyl ring; R₄ is hydroxy orC₁-C₁₆alkoxy; R₅ is hydrogen or

and wherein in formula (Ia) R₉, R₁₀, R₁₁ and R₁₂ are hydrogen; and informula (Ib) R₁₃ is hydrogen; R₁₄ is C₁-C₄alkylthio or N(R₁₇R₁₈); R₁₅ isC₁-C₈alkyl; R₁₆ is phenyl; R₁₇ and R₁₈ are each independently of theother C₁-C₄alkyl or R₁₇ and R₁₈, together with the nitrogen atom towhich they are bonded, form a saturated six-membered ring, which may beinterrupted by —O—; wherein in formula II R₂₁ is phenyl and R₂₂ isC₁-C₁₂alkyl; and wherein in formula III Z is O; R₃₁ and R₃₂ are eachindependently of the other C₁-C₁₈alkyl, phenyl that is unsubstituted ormono- to penta-substituted by C₁-C₈alkyl and/or by C₁-C₈alkoxy, or agroup COR₃₃; and R₃₃ is phenyl that is unsubstituted or mono- totetra-substituted by C₁-C₈alkyl or by C₁-C₈alkoxy.
 4. A processaccording to claim 1 , wherein in the composition the photoinitiator (C)is 1-hydroxy-cyclohexyl-phenyl ketone,1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one or2-hydroxy-2-methyl-1-phenyl-propanone,(4-morpholino-benzoyl)-1-benzyl-1-dimethylamino-propane or(4-methylthiobenzoyl)-1-methyl-1-morpholino-ethane,2,2-dimethoxy-1,2-diphenylethan-1-one,2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide,bis(2,4,6-trimethylbenzoyl)-(2-methylprop-1-yl)-phosphine oxide,bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine -oxide or a mixture ofbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone, hydroxy-2-methyl-1-phenyl-propanoneor 2-methoxy-1-phenyl-ethane-1,2-dione; or ofbis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone, hydroxy-2-methyl-1-phenyl-propanoneor 2-methoxy-1-phenyl-ethane-1,2-dione; or of2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide with1-hydroxy-cyclohexyl-phenyl ketone, hydroxy-2-methyl-1-phenyl-propanoneor 2-methoxy-1-phenyl-ethane-1,2-dione.
 5. A process according to claim1 , wherein a composition comprising (A) polyester polyol, acrylatepolyol or hexamethoxymethylmelamine and (B) isocyanurate orOH-functionalised acrylate and (C) 1-hydroxy-cyclohexyl-phenyl ketone or25% bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide and75% 1-hydroxy-cyclohexyl-phenyl ketone or4[(2-hydroxyethoxy)-benzoyl]-1-hydroxy-1-methyl-ethane, is used.
 6. Aprocess according to claim 1 , wherein the composition contains from0.05 to 20%, especially from 2 to 10%, photoinitiator (C), based on 100parts of component (A).
 7. A process according to claim 1 , wherein thecomposition contains from 1 to 50%, especially from 5 to 30%, component(B), based on 100 parts of component (A).
 8. A process according toclaim 1 , wherein the composition is a composition based onacrylate/melamine, 2-component polyurethane, 1-component polyurethane,2-component epoxy or 1-component epoxy/carboxy.
 9. A process accordingto claim 1 , wherein the spacer group in component (B) is a group

wherein y≧2.
 10. A composition comprising (A) a coating system based on(I) a polyester polyol with melamine or (II) a polyacrylate polyoland/or polyester polyol with a blocked or unblocked polyisocyanate or(III) a carboxyl-, anhydride- or amino-functional polyester and/orpolyacrylate with an epoxy-functional polyester or polyacrylate, or (IV)a mixture of (I), (II), (III) and/or (IV), (B) an OH—, NH₂—, COOH—,epoxy- or NCO-functional resin containing, in addition, at least oneethylenically unsaturated double bond, it being necessary for a spacergroup of at least 4 linearly linked atoms to be present between thedouble bond and the functional group, wherein components (A) and (B) donot contain halogen, and (C) at least one photoinitiator.
 11. The use ofthe composition according to claim 10 as a coating.
 12. Use according toclaim 11 as a finishing lacquer for furniture and in the automobileindustry.
 13. A process for the coating of a substrate, wherein acomposition according to claim 10 is applied to the surface of thesubstrate, is thermally cured and is then irradiated with UV light.